#ifndef __GATT_H__
#define __GATT_H__

#include "bt_common.h"
#include "uuid.h"
#include "conn.h"

/** GATT attribute permission bit field values */
enum bt_gatt_perm
{
    /** No operations supported, e.g. for notify-only */
    BT_GATT_PERM_NONE = 0,

    /** Attribute read permission. */
    BT_GATT_PERM_READ = BIT(0),

    /** Attribute write permission. */
    BT_GATT_PERM_WRITE = BIT(1),

    /** @brief Attribute read permission with encryption.
     *
     *  If set, requires encryption for read access.
     */
    BT_GATT_PERM_READ_ENCRYPT = BIT(2),

    /** @brief Attribute write permission with encryption.
     *
     *  If set, requires encryption for write access.
     */
    BT_GATT_PERM_WRITE_ENCRYPT = BIT(3),

    /** @brief Attribute read permission with authentication.
     *
     *  If set, requires encryption using authenticated link-key for read
     *  access.
     */
    BT_GATT_PERM_READ_AUTHEN = BIT(4),

    /** @brief Attribute write permission with authentication.
     *
     *  If set, requires encryption using authenticated link-key for write
     *  access.
     */
    BT_GATT_PERM_WRITE_AUTHEN = BIT(5),

    /** @brief Attribute prepare write permission.
     *
     *  If set, allows prepare writes with use of BT_GATT_WRITE_FLAG_PREPARE
     *  passed to write callback.
     */
    BT_GATT_PERM_PREPARE_WRITE = BIT(6),

    /** @brief Attribute read permission with LE Secure Connection encryption.
     *
     *  If set, requires that LE Secure Connections is used for read access.
     */
    BT_GATT_PERM_READ_LESC = BIT(7),

    /** @brief Attribute write permission with LE Secure Connection encryption.
     *
     *  If set, requires that LE Secure Connections is used for write access.
     */
    BT_GATT_PERM_WRITE_LESC = BIT(8),
};

/**
 *  @brief Construct error return value for attribute read and write callbacks.
 *
 *  @param _att_err ATT error code
 *
 *  @return Appropriate error code for the attribute callbacks.
 */
#define BT_GATT_ERR(_att_err) (-(_att_err))

/** GATT attribute write flags */
enum
{
    /** @brief Attribute prepare write flag
     *
     * If set, write callback should only check if the device is
     * authorized but no data shall be written.
     */
    BT_GATT_WRITE_FLAG_PREPARE = BIT(0),

    /** @brief Attribute write command flag
     *
     * If set, indicates that write operation is a command (Write without
     * response) which doesn't generate any response.
     */
    BT_GATT_WRITE_FLAG_CMD = BIT(1),

    /** @brief Attribute write execute flag
     *
     * If set, indicates that write operation is a execute, which indicates
     * the end of a long write, and will come after 1 or more
     * @ref BT_GATT_WRITE_FLAG_PREPARE.
     */
    BT_GATT_WRITE_FLAG_EXECUTE = BIT(2),
};

/* Forward declaration of GATT Attribute structure */
struct bt_gatt_attr;

/** @typedef bt_gatt_attr_read_func_t
 *  @brief Attribute read callback
 *
 *  The callback can also be used locally to read the contents of the
 *  attribute in which case no connection will be set.
 *
 *  @param conn   The connection that is requesting to read
 *  @param attr   The attribute that's being read
 *  @param buf    Buffer to place the read result in
 *  @param len    Length of data to read
 *  @param offset Offset to start reading from
 *
 *  @return Number of bytes read, or in case of an error
 *          BT_GATT_ERR() with a specific BT_ATT_ERR_* error code.
 */
typedef ssize_t (*bt_gatt_attr_read_func_t)(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                                            void *buf, uint16_t len, uint16_t offset);

/** @typedef bt_gatt_attr_write_func_t
 *  @brief Attribute write callback
 *
 *  @param conn   The connection that is requesting to write
 *  @param attr   The attribute that's being written
 *  @param buf    Buffer with the data to write
 *  @param len    Number of bytes in the buffer
 *  @param offset Offset to start writing from
 *  @param flags  Flags (BT_GATT_WRITE_FLAG_*)
 *
 *  @return Number of bytes written, or in case of an error
 *          BT_GATT_ERR() with a specific BT_ATT_ERR_* error code.
 */
typedef ssize_t (*bt_gatt_attr_write_func_t)(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                                             const void *buf, uint16_t len, uint16_t offset,
                                             uint8_t flags);

/** @brief GATT Attribute structure. */
struct bt_gatt_attr
{
    /** Attribute UUID */
    const struct bt_uuid *uuid;
    bt_gatt_attr_read_func_t read;
    /** Attribute write callback */
    bt_gatt_attr_write_func_t write;
    /** Attribute user data */
    void *user_data;
    /** Attribute handle */
    uint16_t handle;
    /** @brief Attribute permissions.
     *
     * Will be 0 if returned from bt_gatt_discover().
     */
    uint16_t perm;
};

/** @brief GATT Service structure */
struct bt_gatt_service_static
{
    /** Service Attributes */
    const struct bt_gatt_attr *attrs;
    /** Service Attribute count */
    size_t attr_count;
};

/** @brief GATT Service structure */
struct bt_gatt_service
{
    /** Service Attributes */
    struct bt_gatt_attr *attrs;
    /** Service Attribute count */
    size_t attr_count;

    sys_snode_t node;
};

/** @brief Service Attribute Value. */
struct bt_gatt_service_val
{
    /** Service UUID. */
    const struct bt_uuid *uuid;
    /** Service end handle. */
    uint16_t end_handle;
};

/** @brief Include Attribute Value. */
struct bt_gatt_include
{
    /** Service UUID. */
    const struct bt_uuid *uuid;
    /** Service start handle. */
    uint16_t start_handle;
    /** Service end handle. */
    uint16_t end_handle;
};

/** @brief GATT callback structure. */
struct bt_gatt_cb
{
    /** @brief The maximum ATT MTU on a connection has changed.
     *
     *  This callback notifies the application that the maximum TX or RX
     *  ATT MTU has increased.
     *
     *  @param conn Connection object.
     *  @param tx Updated TX ATT MTU.
     *  @param rx Updated RX ATT MTU.
     */
    void (*att_mtu_updated)(struct bt_conn *conn, uint16_t tx, uint16_t rx);
};

/** Characteristic Properties Bit field values */

/**
 *  @brief Characteristic broadcast property.
 *
 *  If set, permits broadcasts of the Characteristic Value using Server
 *  Characteristic Configuration Descriptor.
 */
#define BT_GATT_CHRC_BROADCAST          0x01
/**
 *  @brief Characteristic read property.
 *
 *  If set, permits reads of the Characteristic Value.
 */
#define BT_GATT_CHRC_READ               0x02
/**
 *  @brief Characteristic write without response property.
 *
 *  If set, permits write of the Characteristic Value without response.
 */
#define BT_GATT_CHRC_WRITE_WITHOUT_RESP 0x04
/**
 *  @brief Characteristic write with response property.
 *
 *  If set, permits write of the Characteristic Value with response.
 */
#define BT_GATT_CHRC_WRITE              0x08
/**
 *  @brief Characteristic notify property.
 *
 *  If set, permits notifications of a Characteristic Value without
 *  acknowledgment.
 */
#define BT_GATT_CHRC_NOTIFY             0x10
/**
 *  @brief Characteristic indicate property.
 *
 * If set, permits indications of a Characteristic Value with acknowledgment.
 */
#define BT_GATT_CHRC_INDICATE           0x20
/**
 *  @brief Characteristic Authenticated Signed Writes property.
 *
 *  If set, permits signed writes to the Characteristic Value.
 */
#define BT_GATT_CHRC_AUTH               0x40
/**
 *  @brief Characteristic Extended Properties property.
 *
 * If set, additional characteristic properties are defined in the
 * Characteristic Extended Properties Descriptor.
 */
#define BT_GATT_CHRC_EXT_PROP           0x80

/** @brief Characteristic Attribute Value. */
struct bt_gatt_chrc
{
    /** Characteristic UUID. */
    const struct bt_uuid *uuid;
    /** Characteristic Value handle. */
    uint16_t value_handle;
    /** Characteristic properties. */
    uint8_t properties;
};

/** Characteristic Extended Properties Bit field values */
#define BT_GATT_CEP_RELIABLE_WRITE 0x0001
#define BT_GATT_CEP_WRITABLE_AUX   0x0002

/** @brief Characteristic Extended Properties Attribute Value. */
struct bt_gatt_cep
{
    /** Characteristic Extended properties */
    uint16_t properties;
};

/** Client Characteristic Configuration Values */

/**
 *  @brief Client Characteristic Configuration Notification.
 *
 *  If set, changes to Characteristic Value shall be notified.
 */
#define BT_GATT_CCC_NOTIFY   0x0001
/**
 *  @brief Client Characteristic Configuration Indication.
 *
 *  If set, changes to Characteristic Value shall be indicated.
 */
#define BT_GATT_CCC_INDICATE 0x0002

/** Client Characteristic Configuration Attribute Value */
struct bt_gatt_ccc
{
    /** Client Characteristic Configuration flags */
    uint16_t flags;
};

/** Server Characteristic Configuration Values */

/**
 *  @brief Server Characteristic Configuration Broadcast
 *
 *  If set, the characteristic value shall be broadcast in the advertising data
 *  when the server is advertising.
 */
#define BT_GATT_SCC_BROADCAST 0x0001

/** Server Characteristic Configuration Attribute Value */
struct bt_gatt_scc
{
    /** Server Characteristic Configuration flags */
    uint16_t flags;
};

/** @brief GATT Characteristic Presentation Format Attribute Value. */
struct bt_gatt_cpf
{
    /** Format of the value of the characteristic */
    uint8_t format;
    /** Exponent field to determine how the value of this characteristic is
     * further formatted
     */
    int8_t exponent;
    /** Unit of the characteristic */
    uint16_t unit;
    /** Name space of the description */
    uint8_t name_space;
    /** Description of the characteristic as defined in a higher layer profile */
    uint16_t description;
};

/**
 * @defgroup bt_gatt_server GATT Server APIs
 * @ingroup bt_gatt
 * @{
 */

/** @brief Register GATT callbacks.
 *
 *  Register callbacks to monitor the state of GATT.
 *
 *  @param cb Callback struct.
 */
void bt_gatt_cb_register(struct bt_gatt_cb *cb);

/** @brief Register GATT service.
 *
 *  Register GATT service. Applications can make use of
 *  macros such as BT_GATT_PRIMARY_SERVICE, BT_GATT_CHARACTERISTIC,
 *  BT_GATT_DESCRIPTOR, etc.
 *
 *  When using @kconfig{CONFIG_BT_SETTINGS} then all services that should have
 *  bond configuration loaded, i.e. CCC values, must be registered before
 *  calling @ref settings_load.
 *
 *  When using @kconfig{CONFIG_BT_GATT_CACHING} and @kconfig{CONFIG_BT_SETTINGS}
 *  then all services that should be included in the GATT Database Hash
 *  calculation should be added before calling @ref settings_load.
 *  All services registered after settings_load will trigger a new database hash
 *  calculation and a new hash stored.
 *
 *  @param svc Service containing the available attributes
 *
 *  @return 0 in case of success or negative value in case of error.
 */
int bt_gatt_service_register(struct bt_gatt_service *svc);

/** @brief Unregister GATT service.
 *
 *  @param svc Service to be unregistered.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
int bt_gatt_service_unregister(struct bt_gatt_service *svc);

/** @brief Check if GATT service is registered.
 *
 *  @param svc Service to be checked.
 *
 *  @return true if registered or false if not register.
 */
bool bt_gatt_service_is_registered(const struct bt_gatt_service *svc);

enum
{
    BT_GATT_ITER_STOP = 0,
    BT_GATT_ITER_CONTINUE,
};

/** @typedef bt_gatt_attr_func_t
 *  @brief Attribute iterator callback.
 *
 *  @param attr Attribute found.
 *  @param handle Attribute handle found.
 *  @param user_data Data given.
 *
 *  @return BT_GATT_ITER_CONTINUE if should continue to the next attribute.
 *  @return BT_GATT_ITER_STOP to stop.
 */
typedef uint8_t (*bt_gatt_attr_func_t)(const struct bt_gatt_attr *attr, uint16_t handle,
                                       void *user_data);

/** @brief Attribute iterator by type.
 *
 *  Iterate attributes in the given range matching given UUID and/or data.
 *
 *  @param start_handle Start handle.
 *  @param end_handle End handle.
 *  @param uuid UUID to match, passing NULL skips UUID matching.
 *  @param attr_data Attribute data to match, passing NULL skips data matching.
 *  @param num_matches Number matches, passing 0 makes it unlimited.
 *  @param func Callback function.
 *  @param user_data Data to pass to the callback.
 */
void bt_gatt_foreach_attr_type(uint16_t start_handle, uint16_t end_handle,
                               const struct bt_uuid *uuid, const void *attr_data,
                               uint16_t num_matches, bt_gatt_attr_func_t func, void *user_data);

/** @brief Attribute iterator.
 *
 *  Iterate attributes in the given range.
 *
 *  @param start_handle Start handle.
 *  @param end_handle End handle.
 *  @param func Callback function.
 *  @param user_data Data to pass to the callback.
 */
static inline void bt_gatt_foreach_attr(uint16_t start_handle, uint16_t end_handle,
                                        bt_gatt_attr_func_t func, void *user_data)
{
    bt_gatt_foreach_attr_type(start_handle, end_handle, NULL, NULL, 0, func, user_data);
}

/** @brief Iterate to the next attribute
 *
 *  Iterate to the next attribute following a given attribute.
 *
 *  @param attr Current Attribute.
 *
 *  @return The next attribute or NULL if it cannot be found.
 */
struct bt_gatt_attr *bt_gatt_attr_next(const struct bt_gatt_attr *attr);

/** @brief Find Attribute by UUID.
 *
 *  Find the attribute with the matching UUID.
 *  To limit the search to a service set the attr to the service attributes and
 *  the attr_count to the service attribute count .
 *
 *  @param attr        Pointer to an attribute that serves as the starting point
 *                     for the search of a match for the UUID.
 *                     Passing NULL will search the entire range.
 *  @param attr_count  The number of attributes from the starting point to
 *                     search for a match for the UUID.
 *                     Set to 0 to search until the end.
 *  @param uuid        UUID to match.
 */
struct bt_gatt_attr *bt_gatt_find_by_uuid(const struct bt_gatt_attr *attr, uint16_t attr_count,
                                          const struct bt_uuid *uuid);

/** @brief Get Attribute handle.
 *
 *  @param attr Attribute object.
 *
 *  @return Handle of the corresponding attribute or zero if the attribute
 *          could not be found.
 */
uint16_t bt_gatt_attr_get_handle(const struct bt_gatt_attr *attr);
// static inline uint16_t bt_gatt_attr_get_handle(const struct bt_gatt_attr *attr)
// {
//     return attr->handle;
// }

/** @brief Get the handle of the characteristic value descriptor.
 *
 * @param attr A Characteristic Attribute.
 *
 * @note The user_data of the attribute must of type @ref bt_gatt_chrc.
 *
 * @return the handle of the corresponding Characteristic Value. The value will
 *         be zero (the invalid handle) if @p attr was not a characteristic
 *         attribute.
 */
uint16_t bt_gatt_attr_value_handle(const struct bt_gatt_attr *attr);
// static inline uint16_t bt_gatt_attr_value_handle(const struct bt_gatt_attr *attr)
// {
//     return (attr->handle + 1);
// }

/** @brief Generic Read Attribute value helper.
 *
 *  Read attribute value from local database storing the result into buffer.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value.
 *  @param buf_len Buffer length.
 *  @param offset Start offset.
 *  @param value Attribute value.
 *  @param value_len Length of the attribute value.
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                          uint16_t buf_len, uint16_t offset, const void *value, uint16_t value_len);

/** @brief Read Service Attribute helper.
 *
 *  Read service attribute value from local database storing the result into
 *  buffer after encoding it.
 *  @note Only use this with attributes which user_data is a bt_uuid.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value read.
 *  @param len Buffer length.
 *  @param offset Start offset.
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_service(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                                  uint16_t len, uint16_t offset);

/**
 *  @brief Statically define and register a service.
 *
 *  Helper macro to statically define and register a service.
 *
 *  @param _name Service name.
 */
#define BT_GATT_SERVICE_DEFINE(_name, ...)                                                         \
    static struct bt_gatt_ccc_cfg cfg_##_name[BT_GATT_CCC_MAX] __unused;                           \
    const struct bt_gatt_attr attr_##_name[] = {__VA_ARGS__};                                      \
    const struct bt_gatt_service_static _name = BT_GATT_SERVICE(attr_##_name)

#define BT_GATT_SERVICE_DEFINE_NC(_name, ...)                                                         \
    static struct bt_gatt_ccc_cfg cfg_##_name[BT_GATT_CCC_MAX] __unused;                           \
    const struct bt_gatt_attr attr_##_name[] __RAM_VAR_SECTION = {__VA_ARGS__};                                      \
    const struct bt_gatt_service_static _name = BT_GATT_SERVICE(attr_##_name)

#define _BT_GATT_ATTRS_ARRAY_DEFINE(n, _instances, _attrs_def)                                     \
    static struct bt_gatt_attr attrs_##n[] = _attrs_def(_instances[n])

#define _BT_GATT_SERVICE_ARRAY_ITEM(_n, _) BT_GATT_SERVICE(attrs_##_n)

/**
 *  @brief Statically define service structure array.
 *
 *  Helper macro to statically define service structure array. Each element
 *  of the array is linked to the service attribute array which is also
 *  defined in this scope using _attrs_def macro.
 *
 *  @param _name         Name of service structure array.
 *  @param _instances    Array of instances to pass as user context to the
 *                       attribute callbacks.
 *  @param _instance_num Number of elements in instance array.
 *  @param _attrs_def    Macro provided by the user that defines attribute
 *                       array for the service. This macro should accept single
 *                       parameter which is the instance context.
 */
#define BT_GATT_SERVICE_INSTANCE_DEFINE(_name, _instances, _instance_num, _attrs_def)              \
    BUILD_ASSERT(ARRAY_SIZE(_instances) == _instance_num,                                          \
                 "The number of array elements does not match its size");                          \
    LISTIFY(_instance_num, _BT_GATT_ATTRS_ARRAY_DEFINE, (;), _instances, _attrs_def);              \
    static struct bt_gatt_service _name[] = {                                                      \
            LISTIFY(_instance_num, _BT_GATT_SERVICE_ARRAY_ITEM, (, ))}

/**
 *  @brief Service Structure Declaration Macro.
 *
 *  Helper macro to declare a service structure.
 *
 *  @param _attrs Service attributes.
 */
#define BT_GATT_SERVICE(_attrs)                                                                    \
    {                                                                                              \
        .attrs = _attrs, .attr_count = ARRAY_SIZE(_attrs),                                         \
    }

/**
 *  @brief Primary Service Declaration Macro.
 *
 *  Helper macro to declare a primary service attribute.
 *
 *  @param _service Service attribute value.
 */
#define BT_GATT_PRIMARY_SERVICE(_service)                                                          \
    BT_GATT_ATTRIBUTE(BT_UUID_GATT_PRIMARY, BT_GATT_PERM_READ, bt_gatt_attr_read_service, NULL,    \
                      _service)

/**
 *  @brief Secondary Service Declaration Macro.
 *
 *  Helper macro to declare a secondary service attribute.
 *
 *  @note A secondary service is only intended to be included from a primary
 *  service or another secondary service or other higher layer specification.
 *
 *  @param _service Service attribute value.
 */
#define BT_GATT_SECONDARY_SERVICE(_service)                                                        \
    BT_GATT_ATTRIBUTE(BT_UUID_GATT_SECONDARY, BT_GATT_PERM_READ, bt_gatt_attr_read_service, NULL,  \
                      _service)

/** @brief Read Include Attribute helper.
 *
 *  Read include service attribute value from local database storing the result
 *  into buffer after encoding it.
 *  @note Only use this with attributes which user_data is a bt_gatt_include.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value read.
 *  @param len Buffer length.
 *  @param offset Start offset.
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_included(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                                   uint16_t len, uint16_t offset);

/**
 *  @brief Include Service Declaration Macro.
 *
 *  Helper macro to declare database internal include service attribute.
 *
 *  @param _service_incl the first service attribute of service to include
 */
#define BT_GATT_INCLUDE_SERVICE(_service_incl)                                                     \
    BT_GATT_ATTRIBUTE(BT_UUID_GATT_INCLUDE, BT_GATT_PERM_READ, bt_gatt_attr_read_included, NULL,   \
                      _service_incl)

/** @brief Read Characteristic Attribute helper.
 *
 *  Read characteristic attribute value from local database storing the result
 *  into buffer after encoding it.
 *  @note Only use this with attributes which user_data is a bt_gatt_chrc.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value read.
 *  @param len Buffer length.
 *  @param offset Start offset.
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_chrc(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                               uint16_t len, uint16_t offset);

#define BT_GATT_CHRC_INIT(_uuid, _handle, _props)                                                  \
    {                                                                                              \
        .uuid = _uuid, .value_handle = _handle, .properties = _props,                              \
    }

/**
 *  @brief Characteristic and Value Declaration Macro.
 *
 *  Helper macro to declare a characteristic attribute along with its
 *  attribute value.
 *
 *  @param _uuid Characteristic attribute uuid.
 *  @param _props Characteristic attribute properties,
 *                a bitmap of BT_GATT_CHRC_* macros.
 *  @param _perm Characteristic Attribute access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 *  @param _read Characteristic Attribute read callback
 *               (@ref bt_gatt_attr_read_func_t).
 *  @param _write Characteristic Attribute write callback
 *                (@ref bt_gatt_attr_write_func_t).
 *  @param _user_data Characteristic Attribute user data.
 */
#define BT_GATT_CHARACTERISTIC(_uuid, _props, _perm, _read, _write, _user_data)                    \
    BT_GATT_ATTRIBUTE(BT_UUID_GATT_CHRC, BT_GATT_PERM_READ, bt_gatt_attr_read_chrc, NULL,          \
                      ((struct bt_gatt_chrc[]){                                                    \
                              BT_GATT_CHRC_INIT(_uuid, 0U, _props),                                \
                      })),                                                                         \
            BT_GATT_ATTRIBUTE(_uuid, _perm, _read, _write, _user_data)

#if defined(CONFIG_BT_CONN)
#define BT_GATT_CCC_MAX (CONFIG_BT_MAX_CONN_NEW)
#else
#define BT_GATT_CCC_MAX 0
#endif

/** @brief GATT CCC configuration entry. */
struct bt_gatt_ccc_cfg
{
    /** Remote peer address. */
    bt_addr_le_t peer;
    /** Configuration value. */
    uint16_t value;
};

/** Internal representation of CCC value */
struct _bt_gatt_ccc
{
    /** Configuration for each connection */
    // struct bt_gatt_ccc_cfg cfg[BT_GATT_CCC_MAX];
    struct bt_gatt_ccc_cfg * cfg;

    /** Highest value of all connected peer's subscriptions */
    uint16_t value;

    /** @brief CCC attribute changed callback
     *
     *  @param attr   The attribute that's changed value
     *  @param value  New value
     */
    void (*cfg_changed)(const struct bt_gatt_attr *attr, uint16_t value);

    /** @brief CCC attribute write validation callback
     *
     *  @param conn   The connection that is requesting to write
     *  @param attr   The attribute that's being written
     *  @param value  CCC value to write
     *
     *  @return Number of bytes to write, or in case of an error
     *          BT_GATT_ERR() with a specific error code.
     */
    ssize_t (*cfg_write)(struct bt_conn *conn, const struct bt_gatt_attr *attr, uint16_t value);

    /** @brief CCC attribute match handler
     *
     *  Indicate if it is OK to send a notification or indication
     *  to the subscriber.
     *
     *  @param conn   The connection that is being checked
     *  @param attr   The attribute that's being checked
     *
     *  @return true  if application has approved notification/indication,
     *          false if application does not approve.
     */
    bool (*cfg_match)(struct bt_conn *conn, const struct bt_gatt_attr *attr);
};

/** @brief Read Client Characteristic Configuration Attribute helper.
 *
 *  Read CCC attribute value from local database storing the result into buffer
 *  after encoding it.
 *
 *  @note Only use this with attributes which user_data is a _bt_gatt_ccc.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value read.
 *  @param len Buffer length.
 *  @param offset Start offset.
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_ccc(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                              uint16_t len, uint16_t offset);

/** @brief Write Client Characteristic Configuration Attribute helper.
 *
 *  Write value in the buffer into CCC attribute.
 *
 *  @note Only use this with attributes which user_data is a _bt_gatt_ccc.
 *
 *  @param conn Connection object.
 *  @param attr Attribute to read.
 *  @param buf Buffer to store the value read.
 *  @param len Buffer length.
 *  @param offset Start offset.
 *  @param flags Write flags.
 *
 *  @return number of bytes written in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_write_ccc(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                               const void *buf, uint16_t len, uint16_t offset, uint8_t flags);

/**
 *  @brief Initialize Client Characteristic Configuration Declaration Macro.
 *
 *  Helper macro to initialize a Managed CCC attribute value.
 *
 *  @param _changed Configuration changed callback.
 *  @param _write Configuration write callback.
 *  @param _match Configuration match callback.
 */
#define BT_GATT_CCC_INITIALIZER(_name, _changed, _write, _match)                                          \
    {                                                                                              \
        .cfg = cfg_##_name, .cfg_changed = _changed, .cfg_write = _write, .cfg_match = _match,              \
    }

/**
 *  @brief Managed Client Characteristic Configuration Declaration Macro.
 *
 *  Helper macro to declare a Managed CCC attribute.
 *
 *  @param _ccc CCC attribute user data, shall point to a _bt_gatt_ccc.
 *  @param _perm CCC access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 */
#define BT_GATT_CCC_MANAGED(_ccc, _perm)                                                           \
    BT_GATT_ATTRIBUTE(BT_UUID_GATT_CCC, _perm, bt_gatt_attr_read_ccc, bt_gatt_attr_write_ccc, _ccc)

/**
 *  @brief Client Characteristic Configuration Declaration Macro.
 *
 *  Helper macro to declare a CCC attribute.
 *
 *  @param _changed Configuration changed callback.
 *  @param _perm CCC access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 */
#define BT_GATT_CCC(_name, _changed, _perm)                                                               \
    BT_GATT_CCC_MANAGED(((struct _bt_gatt_ccc[]){BT_GATT_CCC_INITIALIZER(_name, _changed, NULL, NULL)}),  \
                        _perm)


#ifdef CONFIG_BT_SMP
#define BT_GATT_CCC_EXT(_name, _changed, _perm, wrt_cb)                                                               \
    BT_GATT_CCC_MANAGED(((struct _bt_gatt_ccc[]){BT_GATT_CCC_INITIALIZER(_name, _changed, wrt_cb, NULL)}),  \
                        _perm)
#endif


/** @brief Read Characteristic Extended Properties Attribute helper
 *
 *  Read CEP attribute value from local database storing the result into buffer
 *  after encoding it.
 *
 *  @note Only use this with attributes which user_data is a bt_gatt_cep.
 *
 *  @param conn Connection object
 *  @param attr Attribute to read
 *  @param buf Buffer to store the value read
 *  @param len Buffer length
 *  @param offset Start offset
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_cep(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                              uint16_t len, uint16_t offset);

/**
 *  @brief Characteristic Extended Properties Declaration Macro.
 *
 *  Helper macro to declare a CEP attribute.
 *
 *  @param _value Pointer to a struct bt_gatt_cep.
 */
#define BT_GATT_CEP(_value)                                                                        \
    BT_GATT_DESCRIPTOR(BT_UUID_GATT_CEP, BT_GATT_PERM_READ, bt_gatt_attr_read_cep, NULL,           \
                       (void *)_value)

/** @brief Read Characteristic User Description Descriptor Attribute helper
 *
 *  Read CUD attribute value from local database storing the result into buffer
 *  after encoding it.
 *
 *  @note Only use this with attributes which user_data is a NULL-terminated C
 *        string.
 *
 *  @param conn Connection object
 *  @param attr Attribute to read
 *  @param buf Buffer to store the value read
 *  @param len Buffer length
 *  @param offset Start offset
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_cud(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                              uint16_t len, uint16_t offset);

/**
 *  @brief Characteristic User Format Descriptor Declaration Macro.
 *
 *  Helper macro to declare a CUD attribute.
 *
 *  @param _value User description NULL-terminated C string.
 *  @param _perm Descriptor attribute access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 */
#define BT_GATT_CUD(_value, _perm)                                                                 \
    BT_GATT_DESCRIPTOR(BT_UUID_GATT_CUD, _perm, bt_gatt_attr_read_cud, NULL, (void *)_value)

/** @brief Read Characteristic Presentation format Descriptor Attribute helper
 *
 *  Read CPF attribute value from local database storing the result into buffer
 *  after encoding it.
 *
 *  @note Only use this with attributes which user_data is a bt_gatt_pf.
 *
 *  @param conn Connection object
 *  @param attr Attribute to read
 *  @param buf Buffer to store the value read
 *  @param len Buffer length
 *  @param offset Start offset
 *
 *  @return number of bytes read in case of success or negative values in
 *          case of error.
 */
ssize_t bt_gatt_attr_read_cpf(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf,
                              uint16_t len, uint16_t offset);

/**
 *  @brief Characteristic Presentation Format Descriptor Declaration Macro.
 *
 *  Helper macro to declare a CPF attribute.
 *
 *  @param _value Pointer to a struct bt_gatt_cpf.
 */
#define BT_GATT_CPF(_value)                                                                        \
    BT_GATT_DESCRIPTOR(BT_UUID_GATT_CPF, BT_GATT_PERM_READ, bt_gatt_attr_read_cpf, NULL,           \
                       (void *)_value)

/**
 *  @brief Descriptor Declaration Macro.
 *
 *  Helper macro to declare a descriptor attribute.
 *
 *  @param _uuid Descriptor attribute uuid.
 *  @param _perm Descriptor attribute access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 *  @param _read Descriptor attribute read callback
 *               (@ref bt_gatt_attr_read_func_t).
 *  @param _write Descriptor attribute write callback
 *                (@ref bt_gatt_attr_write_func_t).
 *  @param _user_data Descriptor attribute user data.
 */
#define BT_GATT_DESCRIPTOR(_uuid, _perm, _read, _write, _user_data)                                \
    BT_GATT_ATTRIBUTE(_uuid, _perm, _read, _write, _user_data)

/**
 *  @brief Attribute Declaration Macro.
 *
 *  Helper macro to declare an attribute.
 *
 *  @param _uuid Attribute uuid.
 *  @param _perm Attribute access permissions,
 *               a bitmap of @ref bt_gatt_perm values.
 *  @param _read Attribute read callback (@ref bt_gatt_attr_read_func_t).
 *  @param _write Attribute write callback (@ref bt_gatt_attr_write_func_t).
 *  @param _user_data Attribute user data.
 */
#define BT_GATT_ATTRIBUTE(_uuid, _perm, _read, _write, _user_data)                                 \
    {                                                                                              \
        .uuid = _uuid, .read = _read, .write = _write, .user_data = _user_data, .handle = 0,       \
        .perm = _perm,                                                                             \
    }

/** @brief Notification complete result callback.
 *
 *  @param conn Connection object.
 *  @param user_data Data passed in by the user.
 */
typedef void (*bt_gatt_complete_func_t)(struct bt_conn *conn, void *user_data);

struct bt_gatt_notify_params
{
    /** @brief Notification Attribute UUID type
     *
     *  Optional, use to search for an attribute with matching UUID when
     *  the attribute object pointer is not known.
     */
    const struct bt_uuid *uuid;
    /** @brief Notification Attribute object
     *
     *  Optional if uuid is provided, in this case it will be used as start
     *  range to search for the attribute with the given UUID.
     */
    const struct bt_gatt_attr *attr;
    /** Notification Value data */
    const void *data;
    /** Notification Value length */
    uint16_t len;
    /** Notification Value callback */
    bt_gatt_complete_func_t func;
    /** Notification Value callback user data */
    void *user_data;
#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief Notify attribute value change.
 *
 *  This function works in the same way as @ref bt_gatt_notify.
 *  With the addition that after sending the notification the
 *  callback function will be called.
 *
 *  The callback is run from System Workqueue context.
 *  When called from the System Workqueue context this API will not wait for
 *  resources for the callback but instead return an error.
 *  The number of pending callbacks can be increased with the
 *  @kconfig{CONFIG_BT_CONN_TX_MAX} option.
 *
 *  Alternatively it is possible to notify by UUID by setting it on the
 *  parameters, when using this method the attribute if provided is used as the
 *  start range when looking up for possible matches.
 *
 *  @param conn Connection object.
 *  @param params Notification parameters.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
int bt_gatt_notify_cb(struct bt_conn *conn, struct bt_gatt_notify_params *params);

/** @brief Send multiple notifications in a single PDU.
 *
 *  The GATT Server will send a single ATT_MULTIPLE_HANDLE_VALUE_NTF PDU
 *  containing all the notifications passed to this API.
 *
 *  All `params` must have the same `func` and `user_data` (due to
 *  implementation limitation). But `func(user_data)` will be invoked for each
 *  parameter.
 *
 *  As this API may block to wait for Bluetooth Host resources, it is not
 *  recommended to call it from a cooperative thread or a Bluetooth callback.
 *
 *  The peer's GATT Client must write to this device's Client Supported Features
 *  attribute and set the bit for Multiple Handle Value Notifications before
 *  this API can be used.
 *
 *  Only use this API to force the use of the ATT_MULTIPLE_HANDLE_VALUE_NTF PDU.
 *  For standard applications, `bt_gatt_notify_cb` is preferred, as it will use
 *  this PDU if supported and automatically fallback to ATT_HANDLE_VALUE_NTF
 *  when not supported by the peer.
 *
 *  This API has an additional limitation: it only accepts valid attribute
 *  references and not UUIDs like `bt_gatt_notify` and `bt_gatt_notify_cb`.
 *
 *  @param conn
 *    Target client.
 *    Notifying all connected clients by passing `NULL` is not yet supported,
 *    please use `bt_gatt_notify` instead.
 *  @param num_params
 *    Element count of `params` array. Has to be greater than 1.
 *  @param params
 *    Array of notification parameters. It is okay to free this after calling
 *    this function.
 *
 *  @retval 0
 *    Success. The PDU is queued for sending.
 *  @retval -EINVAL
 *    - One of the attribute handles is invalid.
 *    - Only one parameter was passed. This API expects 2 or more.
 *    - Not all `func` were equal or not all `user_data` were equal.
 *    - One of the characteristics is not notifiable.
 *    - An UUID was passed in one of the parameters.
 *  @retval -ERANGE
 *    - The notifications cannot all fit in a single ATT_MULTIPLE_HANDLE_VALUE_NTF.
 *    - They exceed the MTU of all open ATT bearers.
 *  @retval -EPERM
 *    The connection has a lower security level than required by one of the
 *    attributes.
 *  @retval -EOPNOTSUPP
 *    The peer hasn't yet communicated that it supports this PDU type.
 */
int bt_gatt_notify_multiple(struct bt_conn *conn, uint16_t num_params,
                            struct bt_gatt_notify_params params[]);

/** @brief Notify attribute value change.
 *
 *  Send notification of attribute value change, if connection is NULL notify
 *  all peer that have notification enabled via CCC otherwise do a direct
 *  notification only the given connection.
 *
 *  The attribute object on the parameters can be the so called Characteristic
 *  Declaration, which is usually declared with BT_GATT_CHARACTERISTIC followed
 *  by BT_GATT_CCC, or the Characteristic Value Declaration which is
 *  automatically created after the Characteristic Declaration when using
 *  BT_GATT_CHARACTERISTIC.
 *
 *  @param conn Connection object.
 *  @param attr Characteristic or Characteristic Value attribute.
 *  @param data Pointer to Attribute data.
 *  @param len Attribute value length.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
static inline int bt_gatt_notify(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                                 const void *data, uint16_t len)
{
    struct bt_gatt_notify_params params;

    memset(&params, 0, sizeof(params));

    params.attr = attr;
    params.data = data;
    params.len = len;
#if defined(CONFIG_BT_EATT)
    params.chan_opt = BT_ATT_CHAN_OPT_NONE;
#endif /* CONFIG_BT_EATT */

    return bt_gatt_notify_cb(conn, &params);
}

/** @brief Notify attribute value change by UUID.
 *
 *  Send notification of attribute value change, if connection is NULL notify
 *  all peer that have notification enabled via CCC otherwise do a direct
 *  notification only on the given connection.
 *
 *  The attribute object is the starting point for the search of the UUID.
 *
 *  @param conn Connection object.
 *  @param uuid The UUID. If the server contains multiple services with the same
 *              UUID, then the first occurrence, starting from the attr given,
 *              is used.
 *  @param attr Pointer to an attribute that serves as the starting point for
 *              the search of a match for the UUID.
 *  @param data Pointer to Attribute data.
 *  @param len  Attribute value length.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
static inline int bt_gatt_notify_uuid(struct bt_conn *conn, const struct bt_uuid *uuid,
                                      const struct bt_gatt_attr *attr, const void *data,
                                      uint16_t len)
{
    struct bt_gatt_notify_params params;

    memset(&params, 0, sizeof(params));

    params.uuid = uuid;
    params.attr = attr;
    params.data = data;
    params.len = len;
#if defined(CONFIG_BT_EATT)
    params.chan_opt = BT_ATT_CHAN_OPT_NONE;
#endif /* CONFIG_BT_EATT */

    return bt_gatt_notify_cb(conn, &params);
}

/* Forward declaration of the bt_gatt_indicate_params structure */
struct bt_gatt_indicate_params;

/** @typedef bt_gatt_indicate_func_t
 *  @brief Indication complete result callback.
 *
 *  @param conn Connection object.
 *  @param params Indication params object.
 *  @param err ATT error code
 */
typedef void (*bt_gatt_indicate_func_t)(struct bt_conn *conn,
                                        struct bt_gatt_indicate_params *params, uint8_t err);

typedef void (*bt_gatt_indicate_params_destroy_t)(struct bt_gatt_indicate_params *params);

/** @brief GATT Indicate Value parameters */
struct bt_gatt_indicate_params
{
    /** @brief Indicate Attribute UUID type
     *
     *  Optional, use to search for an attribute with matching UUID when
     *  the attribute object pointer is not known.
     */
    const struct bt_uuid *uuid;
    /** @brief Indicate Attribute object
     *
     *  Optional if uuid is provided, in this case it will be used as start
     *  range to search for the attribute with the given UUID.
     */
    const struct bt_gatt_attr *attr;
    /** Indicate Value callback */
    bt_gatt_indicate_func_t func;
    /** Indicate operation complete callback */
    bt_gatt_indicate_params_destroy_t destroy;
    /** Indicate Value data*/
    const void *data;
    /** Indicate Value length*/
    uint16_t len;
    /** Private reference counter */
    uint8_t _ref;
#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief Indicate attribute value change.
 *
 *  Send an indication of attribute value change. if connection is NULL
 *  indicate all peer that have notification enabled via CCC otherwise do a
 *  direct indication only the given connection.
 *
 *  The attribute object on the parameters can be the so called Characteristic
 *  Declaration, which is usually declared with BT_GATT_CHARACTERISTIC followed
 *  by BT_GATT_CCC, or the Characteristic Value Declaration which is
 *  automatically created after the Characteristic Declaration when using
 *  BT_GATT_CHARACTERISTIC.
 *
 *  Alternatively it is possible to indicate by UUID by setting it on the
 *  parameters, when using this method the attribute if provided is used as the
 *  start range when looking up for possible matches.
 *
 *  @note This procedure is asynchronous therefore the parameters need to
 *        remains valid while it is active. The procedure is active until
 *        the destroy callback is run.
 *
 *  @param conn Connection object.
 *  @param params Indicate parameters.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
int bt_gatt_indicate(struct bt_conn *conn, struct bt_gatt_indicate_params *params);

/** @brief Check if connection have subscribed to attribute
 *
 *  Check if connection has subscribed to attribute value change.
 *
 *  The attribute object can be the so called Characteristic Declaration,
 *  which is usually declared with BT_GATT_CHARACTERISTIC followed
 *  by BT_GATT_CCC, or the Characteristic Value Declaration which is
 *  automatically created after the Characteristic Declaration when using
 *  BT_GATT_CHARACTERISTIC, or the Client Characteristic Configuration
 *  Descriptor (CCCD) which is created by BT_GATT_CCC.
 *
 *  @param conn Connection object.
 *  @param attr Attribute object.
 *  @param ccc_type The subscription type, @ref BT_GATT_CCC_NOTIFY and/or
 *                  @ref BT_GATT_CCC_INDICATE.
 *
 *  @return true if the attribute object has been subscribed.
 */
bool bt_gatt_is_subscribed(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                           uint16_t ccc_type);

/** @brief Get ATT MTU for a connection
 *
 *  Get negotiated ATT connection MTU, note that this does not equal the largest
 *  amount of attribute data that can be transferred within a single packet.
 *
 *  @param conn Connection object.
 *
 *  @return MTU in bytes
 */
uint16_t bt_gatt_get_mtu(struct bt_conn *conn);

/** @} */

/**
 * @defgroup bt_gatt_client GATT Client APIs
 * @ingroup bt_gatt
 * @{
 */

/** @brief GATT Exchange MTU parameters */
struct bt_gatt_exchange_params
{
    /** Response callback */
    void (*func)(struct bt_conn *conn, uint8_t err, struct bt_gatt_exchange_params *params);
};

/** @brief Exchange MTU
 *
 *  This client procedure can be used to set the MTU to the maximum possible
 *  size the buffers can hold.
 *
 *  @note Shall only be used once per connection.
 *
 *  The Response comes in callback @p params->func. The callback is run from
 *  the context specified by 'config BT_RECV_CONTEXT'.
 *  @p params must remain valid until start of callback.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Exchange MTU parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->func on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 *
 *  @retval -EALREADY The MTU exchange procedure has been already performed.
 */
int bt_gatt_exchange_mtu(struct bt_conn *conn, struct bt_gatt_exchange_params *params);

struct bt_gatt_discover_params;

/** @typedef bt_gatt_discover_func_t
 *  @brief Discover attribute callback function.
 *
 *  @param conn Connection object.
 *  @param attr Attribute found, or NULL if not found.
 *  @param params Discovery parameters given.
 *
 *  If discovery procedure has completed this callback will be called with
 *  attr set to NULL. This will not happen if procedure was stopped by returning
 *  BT_GATT_ITER_STOP.
 *
 *  The attribute object as well as its UUID and value objects are temporary and
 *  must be copied to in order to cache its information.
 *  Only the following fields of the attribute contains valid information:
 *   - uuid      UUID representing the type of attribute.
 *   - handle    Handle in the remote database.
 *   - user_data The value of the attribute, if the discovery type maps to an
 *               ATT operation that provides this information. NULL otherwise.
 *               See below.
 *
 *  The effective type of @c attr->user_data is determined by @c params. Note
 *  that the fields @c params->type and @c params->uuid are left unchanged by
 *  the discovery procedure.
 *
 *  @c params->type                      | @c params->uuid         | Type of @c attr->user_data
 *  -------------------------------------|-------------------------|---------------------------
 *  @ref BT_GATT_DISCOVER_PRIMARY        | any                     | @ref bt_gatt_service_val
 *  @ref BT_GATT_DISCOVER_SECONDARY      | any                     | @ref bt_gatt_service_val
 *  @ref BT_GATT_DISCOVER_INCLUDE        | any                     | @ref bt_gatt_include
 *  @ref BT_GATT_DISCOVER_CHARACTERISTIC | any                     | @ref bt_gatt_chrc
 *  @ref BT_GATT_DISCOVER_STD_CHAR_DESC  | @ref BT_UUID_GATT_CEP   | @ref bt_gatt_cep
 *  @ref BT_GATT_DISCOVER_STD_CHAR_DESC  | @ref BT_UUID_GATT_CCC   | @ref bt_gatt_ccc
 *  @ref BT_GATT_DISCOVER_STD_CHAR_DESC  | @ref BT_UUID_GATT_SCC   | @ref bt_gatt_scc
 *  @ref BT_GATT_DISCOVER_STD_CHAR_DESC  | @ref BT_UUID_GATT_CPF   | @ref bt_gatt_cpf
 *  @ref BT_GATT_DISCOVER_DESCRIPTOR     | any                     | NULL
 *  @ref BT_GATT_DISCOVER_ATTRIBUTE      | any                     | NULL
 *
 *  Also consider if using read-by-type instead of discovery is more convenient.
 *  See @ref bt_gatt_read with @ref bt_gatt_read_params.handle_count set to
 *  @c 0.
 *
 *  @return BT_GATT_ITER_CONTINUE to continue discovery procedure.
 *  @return BT_GATT_ITER_STOP to stop discovery procedure.
 */
typedef uint8_t (*bt_gatt_discover_func_t)(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                                           struct bt_gatt_discover_params *params);

/** GATT Discover types */
enum
{
    /** Discover Primary Services. */
    BT_GATT_DISCOVER_PRIMARY,
    /** Discover Secondary Services. */
    BT_GATT_DISCOVER_SECONDARY,
    /** Discover Included Services. */
    BT_GATT_DISCOVER_INCLUDE,
    /** @brief Discover Characteristic Values.
     *
     *  Discover Characteristic Value and its properties.
     */
    BT_GATT_DISCOVER_CHARACTERISTIC,
    /** @brief Discover Descriptors.
     *
     *  Discover Attributes which are not services or characteristics.
     *
     *  @note The use of this type of discover is not recommended for
     *        discovering in ranges across multiple services/characteristics
     *        as it may incur in extra round trips.
     */
    BT_GATT_DISCOVER_DESCRIPTOR,
    /** @brief Discover Attributes.
     *
     *  Discover Attributes of any type.
     *
     *  @note The use of this type of discover is not recommended for
     *        discovering in ranges across multiple services/characteristics
     *        as it may incur in more round trips.
     */
    BT_GATT_DISCOVER_ATTRIBUTE,
    /** @brief Discover standard characteristic descriptor values.
     *
     *  Discover standard characteristic descriptor values and their
     *  properties.
     *  Supported descriptors:
     *   - Characteristic Extended Properties
     *   - Client Characteristic Configuration
     *   - Server Characteristic Configuration
     *   - Characteristic Presentation Format
     */
    BT_GATT_DISCOVER_STD_CHAR_DESC,
};

/** @brief GATT Discover Attributes parameters */
struct bt_gatt_discover_params
{
    /** Discover UUID type */
    const struct bt_uuid *uuid;
    /** Discover attribute callback */
    bt_gatt_discover_func_t func;
    union
    {
        struct
        {
            /** Include service attribute declaration handle */
            uint16_t attr_handle;
            /** Included service start handle */
            uint16_t start_handle;
            /** Included service end handle */
            uint16_t end_handle;
        } _included;
        /** Discover start handle */
        uint16_t start_handle;
    };
    /** Discover end handle */
    uint16_t end_handle;
    /** Discover type */
    uint8_t type;
#if defined(CONFIG_BT_GATT_AUTO_DISCOVER_CCC)
    /** Only for stack-internal use, used for automatic discovery. */
    struct bt_gatt_subscribe_params *sub_params;
#endif /* defined(CONFIG_BT_GATT_AUTO_DISCOVER_CCC) */
#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief GATT Discover function
 *
 *  This procedure is used by a client to discover attributes on a server.
 *
 *  Primary Service Discovery: Procedure allows to discover primary services
 *                             either by Discover All Primary Services or
 *                             Discover Primary Services by Service UUID.
 *  Include Service Discovery: Procedure allows to discover all Include Services
 *                             within specified range.
 *  Characteristic Discovery:  Procedure allows to discover all characteristics
 *                             within specified handle range as well as
 *                             discover characteristics with specified UUID.
 *  Descriptors Discovery:     Procedure allows to discover all characteristic
 *                             descriptors within specified range.
 *
 *  For each attribute found the callback is called which can then decide
 *  whether to continue discovering or stop.
 *
 *  The Response comes in callback @p params->func. The callback is run from
 *  the BT RX thread. @p params must remain valid until start of callback where
 *  iter `attr` is `NULL` or callback will return `BT_GATT_ITER_STOP`.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Discover parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->func on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_discover(struct bt_conn *conn, struct bt_gatt_discover_params *params);

struct bt_gatt_read_params;

/** @typedef bt_gatt_read_func_t
 *  @brief Read callback function
 *
 *  @param conn Connection object.
 *  @param err ATT error code.
 *  @param params Read parameters used.
 *  @param data Attribute value data. NULL means read has completed.
 *  @param length Attribute value length.
 *
 *  @return BT_GATT_ITER_CONTINUE if should continue to the next attribute.
 *  @return BT_GATT_ITER_STOP to stop.
 */
typedef uint8_t (*bt_gatt_read_func_t)(struct bt_conn *conn, uint8_t err,
                                       struct bt_gatt_read_params *params, const void *data,
                                       uint16_t length);

/** @brief GATT Read parameters */
struct bt_gatt_read_params
{
    /** Read attribute callback. */
    bt_gatt_read_func_t func;
    /** If equals to 1 single.handle and single.offset are used.
     *  If greater than 1 multiple.handles are used.
     *  If equals to 0 by_uuid is used for Read Using Characteristic UUID.
     */
    size_t handle_count;
    union
    {
        struct
        {
            /** Attribute handle. */
            uint16_t handle;
            /** Attribute data offset. */
            uint16_t offset;
        } single;
        struct
        {
            /** Attribute handles to read with Read Multiple
             *  Characteristic Values.
             */
            uint16_t *handles;
            /** If true use Read Multiple Variable Length
             *  Characteristic Values procedure.
             *  The values of the set of attributes may be of
             *  variable or unknown length.
             *  If false use Read Multiple Characteristic Values
             *  procedure.
             *  The values of the set of attributes must be of a
             *  known fixed length, with the exception of the last
             *  value that can have a variable length.
             */
            bool variable;
        } multiple;
        struct
        {
            /** First requested handle number. */
            uint16_t start_handle;
            /** Last requested handle number. */
            uint16_t end_handle;
            /** 2 or 16 octet UUID. */
            const struct bt_uuid *uuid;
        } by_uuid;
    };
#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief Read Attribute Value by handle
 *
 *  This procedure read the attribute value and return it to the callback.
 *
 *  When reading attributes by UUID the callback can be called multiple times
 *  depending on how many instances of given the UUID exists with the
 *  start_handle being updated for each instance.
 *
 *  If an instance does contain a long value which cannot be read entirely the
 *  caller will need to read the remaining data separately using the handle and
 *  offset.
 *
 *  The Response comes in callback @p params->func. The callback is run from
 *  the context specified by 'config BT_RECV_CONTEXT'.
 *  @p params must remain valid until start of callback.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Read parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->func on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_read(struct bt_conn *conn, struct bt_gatt_read_params *params);

struct bt_gatt_write_params;

/** @typedef bt_gatt_write_func_t
 *  @brief Write callback function
 *
 *  @param conn Connection object.
 *  @param err ATT error code.
 *  @param params Write parameters used.
 */
typedef void (*bt_gatt_write_func_t)(struct bt_conn *conn, uint8_t err,
                                     struct bt_gatt_write_params *params);

/** @brief GATT Write parameters */
struct bt_gatt_write_params
{
    /** Response callback */
    bt_gatt_write_func_t func;
    /** Attribute handle */
    uint16_t handle;
    /** Attribute data offset */
    uint16_t offset;
    /** Data to be written */
    const void *data;
    /** Length of the data */
    uint16_t length;
#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief Write Attribute Value by handle
 *
 *  The Response comes in callback @p params->func. The callback is run from
 *  the context specified by 'config BT_RECV_CONTEXT'.
 *  @p params must remain valid until start of callback.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from Bluetooth event context. When called from Bluetooth context,
 *  this function will instead instead return `-ENOMEM` if it would block to
 *  avoid a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Write parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->func on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside Bluetooth event context to get blocking behavior. Queue size is
 *  controlled by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_write(struct bt_conn *conn, struct bt_gatt_write_params *params);

/** @brief Write Attribute Value by handle without response with callback.
 *
 *  This function works in the same way as @ref bt_gatt_write_without_response.
 *  With the addition that after sending the write the callback function will be
 *  called.
 *
 *  The callback is run from System Workqueue context.
 *  When called from the System Workqueue context this API will not wait for
 *  resources for the callback but instead return an error.
 *  The number of pending callbacks can be increased with the
 *  @kconfig{CONFIG_BT_CONN_TX_MAX} option.
 *
 *  @note By using a callback it also disable the internal flow control
 *        which would prevent sending multiple commands without waiting for
 *        their transmissions to complete, so if that is required the caller
 *        shall not submit more data until the callback is called.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param handle Attribute handle.
 *  @param data Data to be written.
 *  @param length Data length.
 *  @param sign Whether to sign data
 *  @param func Transmission complete callback.
 *  @param user_data User data to be passed back to callback.
 *
 *  @retval 0 Successfully queued request.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_write_without_response_cb(struct bt_conn *conn, uint16_t handle, const void *data,
                                      uint16_t length, bool sign, bt_gatt_complete_func_t func,
                                      void *user_data);

/** @brief Write Attribute Value by handle without response
 *
 *  This procedure write the attribute value without requiring an
 *  acknowledgment that the write was successfully performed
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param handle Attribute handle.
 *  @param data Data to be written.
 *  @param length Data length.
 *  @param sign Whether to sign data
 *
 *  @retval 0 Successfully queued request.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
static inline int bt_gatt_write_without_response(struct bt_conn *conn, uint16_t handle,
                                                 const void *data, uint16_t length, bool sign)
{
    return bt_gatt_write_without_response_cb(conn, handle, data, length, sign, NULL, NULL);
}

struct bt_gatt_subscribe_params;

/** @typedef bt_gatt_notify_func_t
 *  @brief Notification callback function
 *
 *  In the case of an empty notification, the @p data pointer will be non-NULL
 *  while the @p length will be 0, which is due to the special case where
 *  a @p data NULL pointer means unsubscribed.
 *
 *  @param conn Connection object. May be NULL, indicating that the peer is
 *              being unpaired
 *  @param params Subscription parameters.
 *  @param data Attribute value data. If NULL then subscription was removed.
 *  @param length Attribute value length.
 *
 *  @return BT_GATT_ITER_CONTINUE to continue receiving value notifications.
 *          BT_GATT_ITER_STOP to unsubscribe from value notifications.
 */
typedef uint8_t (*bt_gatt_notify_func_t)(struct bt_conn *conn,
                                         struct bt_gatt_subscribe_params *params, const void *data,
                                         uint16_t length);

/** @typedef bt_gatt_subscribe_func_t
 *  @brief Subscription callback function
 *
 *  @param conn Connection object.
 *  @param err ATT error code.
 *  @param params Subscription parameters used.
 */
typedef void (*bt_gatt_subscribe_func_t)(struct bt_conn *conn, uint8_t err,
                                         struct bt_gatt_subscribe_params *params);

/** Subscription flags */
enum
{
    /** @brief Persistence flag
     *
     *  If set, indicates that the subscription is not saved
     *  on the GATT server side. Therefore, upon disconnection,
     *  the subscription will be automatically removed
     *  from the client's subscriptions list and
     *  when the client reconnects, it will have to
     *  issue a new subscription.
     */
    BT_GATT_SUBSCRIBE_FLAG_VOLATILE,

    /** @brief No resubscribe flag
     *
     *  By default when BT_GATT_SUBSCRIBE_FLAG_VOLATILE is unset, the
     *  subscription will be automatically renewed when the client
     *  reconnects, as a workaround for GATT servers that do not persist
     *  subscriptions.
     *
     *  This flag will disable the automatic resubscription. It is useful
     *  if the application layer knows that the GATT server remembers
     *  subscriptions from previous connections and wants to avoid renewing
     *  the subscriptions.
     */
    BT_GATT_SUBSCRIBE_FLAG_NO_RESUB,

    /** @brief Write pending flag
     *
     *  If set, indicates write operation is pending waiting remote end to
     *  respond.
     *
     *  @note Internal use only.
     */
    BT_GATT_SUBSCRIBE_FLAG_WRITE_PENDING,

    /** @brief Sent flag
     *
     *  If set, indicates that a subscription request (CCC write) has
     *  already been sent in the active connection.
     *
     *  Used to avoid sending subscription requests multiple times when the
     *  @kconfig{CONFIG_BT_GATT_AUTO_RESUBSCRIBE} quirk is enabled.
     *
     *  @note Internal use only.
     */
    BT_GATT_SUBSCRIBE_FLAG_SENT,

    BT_GATT_SUBSCRIBE_NUM_FLAGS
};

/** @brief GATT Subscribe parameters */
struct bt_gatt_subscribe_params
{
    sys_snode_t node;

    /** Notification value callback */
    bt_gatt_notify_func_t notify;
    /** Subscribe CCC write request response callback
     *  If given, called with the subscription parameters given when subscribing
     */
    bt_gatt_subscribe_func_t subscribe;

    /** @deprecated{subscribe CCC write response callback} */
    bt_gatt_write_func_t write;
    /** Subscribe value handle */
    uint16_t value_handle;
    /** Subscribe CCC handle */
    uint16_t ccc_handle;
#if defined(CONFIG_BT_GATT_AUTO_DISCOVER_CCC)
    /** Subscribe End handle (for automatic discovery) */
    uint16_t end_handle;
    /** Discover parameters used when ccc_handle = 0 */
    struct bt_gatt_discover_params *disc_params;
#endif /* CONFIG_BT_GATT_AUTO_DISCOVER_CCC */
    /** Subscribe value */
    uint16_t value;
#if defined(CONFIG_BT_SMP)
    /** Minimum required security for received notification. Notifications
     * and indications received over a connection with a lower security
     * level are silently discarded.
     */
    bt_security_t min_security;
#endif
    /** Subscription flags */
    // ATOMIC_DEFINE(flags, BT_GATT_SUBSCRIBE_NUM_FLAGS);

#if defined(CONFIG_BT_EATT)
    enum bt_att_chan_opt chan_opt;
#endif /* CONFIG_BT_EATT */
};

/** @brief Subscribe Attribute Value Notification
 *
 *  This procedure subscribe to value notification using the Client
 *  Characteristic Configuration handle.
 *  If notification received subscribe value callback is called to return
 *  notified value. One may then decide whether to unsubscribe directly from
 *  this callback. Notification callback with NULL data will not be called if
 *  subscription was removed by this method.
 *
 *  The Response comes in callback @p params->subscribe. The callback is run from
 *  the context specified by 'config BT_RECV_CONTEXT'.
 *  @p params must remain valid until start of callback.
 *  The Notification callback @p params->notify is also called from the BT RX
 *  thread.
 *
 *  @note Notifications are asynchronous therefore the parameters need to
 *        remain valid while subscribed.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Subscribe parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->write on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_subscribe(struct bt_conn *conn, struct bt_gatt_subscribe_params *params);

/** @brief Resubscribe Attribute Value Notification subscription
 *
 *  Resubscribe to Attribute Value Notification when already subscribed from a
 *  previous connection. The GATT server will remember subscription from
 *  previous connections when bonded, so resubscribing can be done without
 *  performing a new subscribe procedure after a power cycle.
 *
 *  @note Notifications are asynchronous therefore the parameters need to
 *        remain valid while subscribed.
 *
 *  @param id     Local identity (in most cases BT_ID_DEFAULT).
 *  @param peer   Remote address.
 *  @param params Subscribe parameters.
 *
 *  @return 0 in case of success or negative value in case of error.
 */
int bt_gatt_resubscribe(uint8_t id, const bt_addr_le_t *peer,
                        struct bt_gatt_subscribe_params *params);

/** @brief Unsubscribe Attribute Value Notification
 *
 *  This procedure unsubscribe to value notification using the Client
 *  Characteristic Configuration handle. Notification callback with NULL data
 *  will be called if subscription was removed by this call, until then the
 *  parameters cannot be reused.
 *
 *  The Response comes in callback @p params->func. The callback is run from
 *  the BT RX thread.
 *
 *  This function will block while the ATT request queue is full, except when
 *  called from the BT RX thread, as this would cause a deadlock.
 *
 *  @param conn Connection object.
 *  @param params Subscribe parameters.
 *
 *  @retval 0 Successfully queued request. Will call @p params->write on
 *  resolution.
 *
 *  @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
 *  Allow a pending request to resolve before retrying, or call this function
 *  outside the BT RX thread to get blocking behavior. Queue size is controlled
 *  by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
 */
int bt_gatt_unsubscribe(struct bt_conn *conn, struct bt_gatt_subscribe_params *params);

/** @brief Try to cancel the first pending request identified by @p params.
 *
 *  This function does not release @p params for reuse. The usual callbacks
 *  for the request still apply. A successful cancel simulates a
 *  #BT_ATT_ERR_UNLIKELY response from the server.
 *
 *  This function can cancel the following request functions:
 *   - #bt_gatt_exchange_mtu
 *   - #bt_gatt_discover
 *   - #bt_gatt_read
 *   - #bt_gatt_write
 *   - #bt_gatt_subscribe
 *   - #bt_gatt_unsubscribe
 *
 *  @param conn The connection the request was issued on.
 *  @param params The address `params` used in the request function call.
 */
void bt_gatt_cancel(struct bt_conn *conn, void *params);

int bt_gatt_service_init(int n, const struct bt_gatt_service_static** service_list);


#define BT_GATT_CENTRAL_ADDR_RES_NOT_SUPP 0
#define BT_GATT_CENTRAL_ADDR_RES_SUPP     1

#define BT_GATT_PERM_READ_MASK                                                                     \
    (BT_GATT_PERM_READ | BT_GATT_PERM_READ_ENCRYPT | BT_GATT_PERM_READ_AUTHEN |                    \
     BT_GATT_PERM_READ_LESC)
#define BT_GATT_PERM_WRITE_MASK                                                                    \
    (BT_GATT_PERM_WRITE | BT_GATT_PERM_WRITE_ENCRYPT | BT_GATT_PERM_WRITE_AUTHEN |                 \
     BT_GATT_PERM_WRITE_LESC)
#define BT_GATT_PERM_ENCRYPT_MASK (BT_GATT_PERM_READ_ENCRYPT | BT_GATT_PERM_WRITE_ENCRYPT)
#define BT_GATT_PERM_AUTHEN_MASK  (BT_GATT_PERM_READ_AUTHEN | BT_GATT_PERM_WRITE_AUTHEN)
#define BT_GATT_PERM_LESC_MASK    (BT_GATT_PERM_READ_LESC | BT_GATT_PERM_WRITE_LESC)
#define BT_GATT_PERM_READ_ENCRYPT_MASK                                                             \
    (BT_GATT_PERM_READ_ENCRYPT | BT_GATT_PERM_READ_AUTHEN | BT_GATT_PERM_READ_LESC)

void bt_gatt_init(void);
void bt_gatt_connected(struct bt_conn *conn);
void bt_gatt_att_max_mtu_changed(struct bt_conn *conn, uint16_t tx, uint16_t rx);
void bt_gatt_encrypt_change(struct bt_conn *conn);
void bt_gatt_disconnected(struct bt_conn *conn);

bool bt_gatt_change_aware(struct bt_conn *conn, bool req);

int bt_gatt_store_ccc(uint8_t id, const bt_addr_le_t *addr);

void bt_gatt_set_subscriptions_buf();
// int bt_gatt_clear(uint8_t id, const bt_addr_le_t *addr);

#if defined(CONFIG_BT_GATT_CLIENT)
void bt_gatt_notification(struct bt_conn *conn, uint16_t handle, const void *data, uint16_t length);

void bt_gatt_mult_notification(struct bt_conn *conn, const void *data, uint16_t length);
#else
// static inline void bt_gatt_notification(struct bt_conn *conn, uint16_t handle, const void *data,
//                                         uint16_t length)
// {
// }

// static inline void bt_gatt_mult_notification(struct bt_conn *conn, const void *data,
//                                              uint16_t length)
// {
// }
#endif /* CONFIG_BT_GATT_CLIENT */

struct bt_gatt_attr;

/* Check attribute permission */
uint8_t bt_gatt_check_perm(struct bt_conn *conn, const struct bt_gatt_attr *attr, uint16_t mask);
uint8_t disconnected_cb(const struct bt_gatt_attr *attr, uint16_t handle, void *user_data);

typedef void (*gatt_conn_disc_cb)(struct bt_conn *conn);
extern gatt_conn_disc_cb  bt_gatt_disconnected_ptr;
extern gatt_conn_disc_cb  bt_gatt_connected_ptr;

struct gatt_sub
{
    uint8_t id;
    bt_addr_le_t peer;
    sys_slist_t list;
};
#endif